Common types of airborne substance detectors include smoke and carbon monoxide detectors. Such devices are typically configured as single detector units that sound an alarm upon detection of a single target substance. Combination airborne substance detectors, by contrast, are capable of sensing, within the same device, the presence of a plurality of target substances.
Combination airborne substance detectors are useful because they provide an efficient means for detecting and warning of the presence of potentially hazardous and/or harmful target substances. For instance, when detecting for a plurality of airborne substances, the use of more than one substance detector is undesirable in that multiple detectors does not allow for optimal placement near potential source(s) of target substances, requires additional power sources or connections, imposes additional space requirements, and can be visually unappealing.
In typical combination detector systems, the detection of one substance has priority over the remaining secondary substance(s). The detection of secondary substances is disabled in typical combination detector systems once the primary substance is detected. The theory of operation in these typical combination detectors is that detection of the primary substance has priority that negates further detection of remaining target substance(s).
A problem associated with typical combination airborne substance detectors is the user is no longer warned of the presence of secondary substances once the primary substance is detected. For airborne substances such as smoke, carbon monoxide or combustible gases, a life-threatening condition can occur for which no warning is given. For instance, in typical combination smoke-carbon monoxide detectors, smoke detection has precedence over carbon monoxide detection. But, in a combination combustible gas-carbon monoxide detector, carbon monoxide detection may have priority over combustible gas detection, thereby potentially endangering a user's health and/or safety. A combustible gas leak, such as a propane leak, requires the user to take immediate action, whereas excess carbon monoxide generally means the user has time to react. If carbon monoxide is detected causing the alarm to emit a warning, and there is further a propane leak, the user will be unaware of the dangerous second condition. For example, in reacting to a carbon monoxide alert, the user may activate an electrical device, such as a fan or light, which could in turn lead to ignition of a combustible gas that is also present in the nearby environment.
A combination airborne substance detector, as disclosed herein, provides advantages over conventional devices by its capability to simultaneously alert a user of multiple life-threatening conditions. Furthermore, in environments where combustible gas(es) and/or other critical conditions involving potentially hazardous airborne substances are present, and for which immediate attention and remedial action is required or desirable, the present combination airborne substance detector provides the additional advantage of being able to initially warn of such critical conditions, followed by warnings of any secondary critical conditions.